A survey of cereal aphids and their natural enemies in winter wheat in 1980.
Experiments by the Glasshouse Crops Research Institute in previous years involving caging and barrier exclusion techniques implicated natural enemies as an important factor in determining cereal aphid numbers in winter wheat. In 1980, a survey of fields on North Farm, Worthing, was carried out to look for effects of natural enemies in the absence of experimental manipulations.
Ten fields of winter wheat were selected on the basis of differences in sowing date, type of edge habitat soil type, altitude and acreage. Five of the fields were early-sown (1.10.79-6.10.79) and five late-sown (24.10.79-1.11.79) and a sampling site was established near the edge (5 m from the field margin) middle of each. Four pitfall traps for polyphagous predators and three water traps for aerial aphid-specific predators at each site were emptied at weekly intervals. Larvae and adults of aphid-specific predators were sampled by taking 200 sweeps per site per week. Parasitoids and entomophagous fungi were assessed by counting mummies and dead diseased aphids on the shoots.